1. Technical Field
The present invention relates to a rope connecting support for use in a crane vehicle when a hoist rope wounded around a winch on a swivel base is stretched along the upper surface of a boom.
2. Related Art
When a large crane vehicle moves on a public road, its boom and winch (sub-winch) sometimes are removed and delivered separately due to a weight limit or height limit. In this case, a hoist rope to be stretched along the upper surface of the boom is wound around the winch. Then, in order to make the crane operational at a workplace, it is necessary to draw the front end side of the hoist rope wounded around the winch to the front end of the boom along the upper surface of the boom.
As shown in FIG. 16, conventionally, in order to draw the front end side of the hoist rope wound around the winch to the front end of the boom along the upper surface of the boom, an operator M1 holds a front end 6b of a hoist rope 6 on a swivel base 2 and walks on a boom 3 to a front end 3b (the position of the operator M2) of the boom 3, reeling out the hoist rope 6 from a winch 5, so that it is possible to bring the front end (6b′) of the hoist rope (6′) to the front end 3b of the boom 3. Then, the front end (6b″) of the hoist rope (6″) is suspended downward via a sheave 33 provided on the front end 3b of the boom 3, so that the hoist rope can be stretched on the upper surface 3c of the boom 3.
However, when the crane vehicle is large, it is dangerous for the operator M1 (M2) to walk on the upper surface 3c of the boom 3, holding the front end 6b′ of the hoist rope 6′. This is because the upper surface 3c of the boom 3 is located in a considerably high position, for example, about 4 m from the ground even if the boom 3 lies (in a horizontal position); and the width of the boom 3 is not very wide (for example, about 60 to 70 cm).
Moreover, conventionally, in order to guard the operator from danger of stretching the hoist rope in a high place, a plurality of stanchions S are mounted to the boom 3 to stretch a safety rope T between the stanchions S as shown in FIG. 16. In this case, it is troublesome and dangerous for the operator to set up the stanchions S and the safety rope T in a high place. Moreover, the stanchions S and the safety rope T still cannot eliminate the danger from the operator to walk on the upper surface 3c of the boom 3, holding the front end 6b of the hoist rope 6 to stretch the hoist rope 6 in a high place.
Incidentally, the applicant filed a method of extending hoisting freight rope in boom detachable crane vehicle (see Patent Literature 1). In this method, the front end side of the hoist rope wound around the winch is drawn to the front end of the boom, along the upper surface of the boom. Here, this method disclosed in Patent Literature 1 is applicable to a crane vehicle having the boom 3 which is separated from the vehicle 1 (swivel base 2) and conveyed by a truck, and then, the boom (3′) is mounted to the swivel base 2 at a workplace, as shown in FIG. 17.
The method disclosed in Patent Literature 1 includes the following steps. First, as shown in FIG. 17, an auxiliary rope 7 having a length from a base end 3a to a front end 3b of the boom 3 (from 7a to 7b) is mounted to the boom 3 separated from the vehicle 1 (swivel base 2), along the upper surface 3c of the boom 3. Here, this auxiliary rope 7 is used to pull the hoist rope 6 being reeled out of the winch 5 and is made of thin string (may be a nylon rope).
Next, as shown in FIG. 17, while the boom 3′ with the auxiliary rope 7′ is mounted on the swivel base 2, the operator M1 rides on the swivel base 2 and connects the front end 6b of the hoist rope 6 reeled out of the winch 5 to a base end 7a′ of the auxiliary rope 7′ for pulling the hoist rope 6 (the connecting portion is shown as “R” in FIG. 18). After that, as shown in FIG. 18, the operator M3 on the ground draws the front end 7c side of the auxiliary rope 7 downward via the sheave 33 provided on the front end 3b of the boom 3, so that the hoist rope 6 reeled out of the winch 5 can be stretched to the front end 3b of the boom 3, along the upper surface 3c of the boom 3. Here, since the area on the swivel base 2 is relatively wide, it is safe for the operator M1 (shown in FIG. 17) to work on the swivel base 2.
As described above, Patent Literature 1 (FIGS. 17 and 18) provides an advantage of eliminating the dangerous work in a high place because the operator has not walk on the upper surface 3c of the boom 3 (in the high place) to stretch the hoist rope 6.
The connection (connecting part R) between the front end 6b of the hoist rope 6 and the base end 7a of the auxiliary rope 7 is made by using an appropriate connector, or by directly connecting the front end 6b and the base end 7a to one another. Here, the connecting part R is considerably large in diameter.
Meanwhile, a plurality of guard members 36 (the number of them is two in FIGS. 17 and 18) are provided on the upper surface 3c of the boom 3 of the crane vehicle, at intervals in the longitudinal direction of the boom 3. As shown in FIG. 19, each of the guard members 36 is formed by right and left upright rods 37, and a connecting rod 38 that connects between the upright rods 37 on the upper surface 3c of the boom 3. This connecting rod 38 is disposed in the width direction of the boom 3, and therefore may become an obstacle to the ropes (including the connecting part R) being moved on the upper surface 3c of the boom 3c. 
Patent literature 1: Japanese Patent Application Laid-Open No. 2012-232805
According to the method disclosed in Patent Literature 1 (FIGS. 17 and 18), the front end 6b of the hoist rope 6 is connected to the base end 7a of the auxiliary rope 7 provided along the upper surface 3c of the boom 3 on the swivel base 2, and then the front end 7c side of the auxiliary rope 7 is drawn down from the ground beneath the front end 3b of the boom 3 as shown in FIG. 18. By this means, it is possible to stretch the hoist rope 6 reeled out of the winch 5 along the upper surface 3c of the boom 3. As a result, the dangerous work in a high place is not needed to stretch the hoist rope 6 on the boom 3. However, when the front end 7c side of the auxiliary rope 7 is drawn down in the state shown in FIG. 18, the connecting part R between the front end 6b of the hoist rope 6 and the base end 7a of the auxiliary rope 7 catches on the obstacle (the connecting rod 38 of the guard member 36 shown in FIG. 19) provided on the upper surface 3c of the boom 3, and therefore may not smoothly get over the obstacle (connecting rod 38). In other words, the connecting part R between the front end 6b of the hoist rope 6 and the base end 7a of the auxiliary rope 7a is considerably large in diameter, and therefore this makes a problem that the connecting part R catches on the obstacle (connecting rod 38) when being moved on the upper surface 3c of the boom 3.